The invention relates to a reversible reciprocating internal combustion engine with intake and exhaust valves.
Reciprocating internal combustion engines are generally operated only in one direction of rotation. If in a certain application, for example, in motor vehicles, motive power in both direction of rotation is needed, the internal combustion engine is generally provided with a reversing transmission, which can be shifted with interruption of the transmission of power or under load.
DE 26 34 916 C2 discloses a reversible piston-type internal combustion engine, which is capable of operating in both directions of rotation. To change its direction of rotation, the internal combustion engine is shut down and stopped and the timing of the intake and exhaust valves is changed for the new direction of rotation by axially moving a camshaft operating the valves so that cams specifically provided for the new direction of operation become effective. In internal combustion engines with external ignition also the ignition timing must be adapted to the new direction of rotation. Reversible internal combustion engines are used especially in connection with ships, particularly ships having low-speed Diesel engines, which drive a ship propeller directly without intermediate transmission. Such reversible arrangements have been successfully used to avoid the need for transmissions and reversing transmissions in drives transmitting high torques and high power. In these application, there is generally sufficient time for reversing the direction of engine rotation. Also, such piston type internal combustion engines can be slowed down and restarted relatively rapidly by pressurized air.
U.S. Pat. No. 39 81 278 discloses an arrangement for the protection of reversible piston type internal combustion engines during rotation reversal of the engine. In this case, the engine speed and the direction of rotation at the time the reversing operation is initiated are determined.
In U.S. Pat. No. 5 036 802, a method is disclosed, whereby the direction of rotation of a two-cycle engine with external ignition can be reversed. During reversal, the ignition is interrupted, the speed of the crankshaft is continuously reduced and, at the same time, monitored. When the speed falls below a predetermined value and before the engine is at a standstill, the ignition is reactivated, but with a sufficiently large ignition angle before the top dead center position of the respective piston that the forces generated are sufficiently large to drive the piston back down before it reaches the top dead center position. Then the engine rotates in the opposite direction and the ignition is set to a normal value corresponding to the new direction of rotation. Such a reversal of engine rotation is to be used in connection with snowmobiles, which change their direction of movement relatively frequently. The reversal of the direction of engine rotation is performed automatically when an operating switch is activated. The internal combustion engine does not need to be stopped for that purpose.
However, the known reversal arrangements and methods are not suitable for motor vehicles with valve controlled reciprocating internal combustion engines.
Electromagnetic actuators for operating gas change (intake and exhaust) valves are generally known for example from DE 39 20 976 Al. They include generally two operating magnets, that is a valve opening magnet and a valve-closing magnet between whose pole faces an armature is arranged so as to be movable coaxially with a valve shaft. The armature acts directly or indirectly on a valve shaft of the gas change valve by way of an armature plunger. Actuators operating in accordance with the principle of a mass oscillator include a pre-tensioned spring mechanism engaging the armature. As spring mechanism generally two pre-tensioned compression springs are used, that is, an upper valve spring which serves as a valve opening spring and which generates a force in valve opening direction and a lower valve spring which serves as a valve closing spring and generates a force in the valve closing direction. If the magnets are not energized, the armature is held by the valve springs in an equilibrium position between the magnets. With such actuators gas change valves can be controlled individually as desired.
It is the object of the present invention to simplify the reversal of rotation of reciprocating internal combustion engines and to make such arrangements suitable for use in motor vehicles with valve controlled engines.